Problem: Khan.scratchpad.disable(); Christopher sells magazine subscriptions and earns $$7$ for every new subscriber he signs up. Christopher also earns a $$25$ weekly bonus regardless of how many magazine subscriptions he sells. If Christopher wants to earn at least $$56$ this week, what is the minimum number of subscriptions he needs to sell?
Answer: To solve this, let's set up an expression to show how much money Christopher will make. Amount earned this week $=$ $ $ Subscriptions sold $\times$ Price per subscription $+$ Weekly bonus Since Christopher wants to make at least $$56$ this week, we can turn this into an inequality. Amount earned this week $\geq $56$ Subscriptions sold $\times$ Price per subscription $+$ Weekly bonus $\geq $56$ We are solving for the number of subscriptions sold, so let subscriptions sold be represented by the variable $x$ We can now plug in: $x \cdot $7 + $25 \geq $56$ $ x \cdot $7 \geq $56 - $25 $ $ x \cdot $7 \geq $31 $ $x \geq \dfrac{31}{7} \approx 4.43$ Since Christopher cannot sell parts of subscriptions, we round $4.43$ up to $5$ Christopher must sell at least 5 subscriptions this week.